This invention relates to a golf ball having a good xe2x80x9cclickxe2x80x9d and xe2x80x9cfeelxe2x80x9d when hit with a golf club.
With its good flight performance and durability, the type of golf ball in most common use today is the solid golf ball composed of a rubber-base core enclosed in a cover.
Solid golf ball of this type, while possessing better flight characteristics than thread-wound golf balls, have in the past had a hard xe2x80x9cfeelxe2x80x9d upon impact. Over the past few years, however, rubber resilience enhancing techniques have been applied to achieve a softer feel without sacrificing flight performance.
While these softer golf balls do have an improved feel, the xe2x80x9cclickxe2x80x9d of the ball when hit with a golf club is dull. Many skilled golfers complain that the click of such balls leaves something to be desired.
Recently, a number of ideas have been proposed for multi-piece golf balls in which the solid core has a multilayer structure comprising an inner layer and an outer layer made of differing materials. Yet, such balls are designed primarily to achieve a softer feel, and do little to resolve the poor click of the ball. Hence, the search has continued for a workable solution to the xe2x80x9cdull clickxe2x80x9d problem associated with softer-type solid golf balls.
Also, golf balls are subject to a number of rules, including strict regulations concerning symmetry. Most commercial multi-piece golf balls are of the multilayer type in which the differing members are arranged concentrically to satisfy the symmetry requirements. As such, improvements in softness have for the most part been achieved through multilayer ball constructions of one sort or another. A constant concern in such constructions is interfacial adhesion between the layers. For instance, where there are large differences in hardness between the layers, interlayer separation and cracking of the constituent members occur.
Therefore, one object of the invention is to provide a golf ball having both a good click and feel. A second object of the invention is to provide a golf ball which, in addition to having a good click and feel, also has excellent symmetry and durability.
We have found that, rather than trying to resolve the problem of a dull click in softer-type solid golf balls by providing the core with a multilayer construction, solid golf balls can be conferred with both a soft feel and a good click by incorporating particles of a specific hardness within the solid core.
A first aspect of the invention thus provides a solid golf ball comprising a solid core and a cover enclosing the core, wherein the core is composed of, in admixture, a solid core-forming material and at least one particle made of a different material, which particle has a Shore D hardness at least 10 units higher than the surface hardness of the core. Preferably, the solid core is made of a rubber composition composed primarily of cis-1,4-polybutadiene and the particle is composed primarily of a thermoplastic resin or a thermoplastic elastomer. The particle typically has a diameter of 1 to 15 mm and a Shore D hardness of 60 to 95. Preferably at least 3 particles are incorporated within the solid core.
Moreover, through investigations aimed at improving the dull click of softer-type solid golf balls and also assuming good symmetry, we have found that by incorporating at least one particle of a different material within the solid core of the ball, restricting the difference in specific gravity between the particle and the core to within a range of xc2x10.1 and making the particle harder than the surface of the core, the particle improves both the feel and click of the ball upon impact without compromising the ball""s resilience or softness of feel, and also confers the ball with good durability and symmetry.
Hence, a second aspect of the invention provides a solid golf ball comprising a solid core and a cover enclosing the core, wherein the core is composed of, in admixture, a solid core-forming material and at least one particle made of a different material, which particle has a specific gravity difference with the core of at most xc2x10.1 and is harder than the surface of the core. Preferably, the solid core is made of a rubber composition composed primarily of cis-1,4-polybutadiene and the particle is composed primarily of a thermoplastic resin or a thermoplastic elastomer. The particle typically has a diameter of 1 to 10 mm.
A further discovery we have made is that if, in order to improve the dull click of a softer-type solid golf ball, at least one particle made of a different material from the core is incorporated within the core in such a way that the particle accounts for 0.1 to 15% of the core volume and is not exposed on the surface of the core, the inclusion of the particle does not induce cracking of the solid core, the influence of the particle""s resilience and hardness upon the ball as a whole is suppressed, and both a good feel and click are achieved. Moreover, the golf ball has an excellent durability.
Accordingly, a third aspect of the invention provides a solid golf ball comprising a solid core and a cover enclosing the core, wherein the core is composed of, in admixture, a solid core-forming material and at least one particle made of a different material, which particle accounts for 0.1 to 15% by volume of the core and is not exposed on the surface of the core. Preferably, the solid core is made of a rubber composition composed primarily of cis-1,4-polybutadiene and the particle is composed primarily of a thermoplastic resin or a thermoplastic elastomer. The particle typically has a diameter of 1 to 13 mm and is located at least 1 mm inside the surface of the core